1. Field of the Invention
The present invention relates to a liquid crystal display apparatus for projecting a picture on a screen with use of a liquid crystal display element, including such as a liquid crystal projector, a liquid crystal television, a projection type display device, and so on, and also relates to an optical device for use therein.
2. Description of Prior Art
Conventionally, in a display apparatus for projecting a picture on a screen with use of a liquid crystal display element, upon the liquid crystal display element of such as a liquid crystal panel or the like, a light is irradiated from a light source, such as a light bulb, etc., and that penetrating or transmitting through it is projected on the screen. And, by adjusting or regulating an amount or quantity of polarization at each pixel in the liquid crystal element, the display is performed or accomplished.
In such the liquid crystal display apparatus, upon a requirement from a user of obtaining a good projection picture even in a bright circumstance or place, conventionally, an attempt was made to rise up an optical output of the projected picture has been tries by enhancement in a brightness of the light source and/or by improvement in an utility efficiency of the light beam thereof. For instance, with a technology described in Japanese Patent Laying-Open No. Sho 63-197913 (1988), there are utilized a polarization conversion element which comprises a polarized light separation means for dividing or separating an irregular polarized light from the light source into two (2) polarized lights being orthogonal to each other, and a polarization direction rotating means for rotating one of the polarized lights separated into a direction consistent with that of the other polarized light, thereby improving or increasing the utility efficiency of the light.
By the way, in the liquid crystal display apparatus as mentioned in the above, within the light emitted from the light source, the light except that being projected finally is absorbed into the liquid crystal display element and optical elements and so on, in periphery thereof, and it comes into heat. Therefore, the liquid crystal display element and the optical elements and so on in the periphery thereof are heated therewith. In particular, the rise-up in the output of the projection light, for purpose of increasing the brightness of the light source and/or of improving the utility efficiency of the light, results into the increase in light amount being incident upon the liquid crystal display element, and also leads to the increase in the heat generation of the liquid crystal display element and polarizing plates. Further, in a case where such the polarization conversion element is used within an optical system reaching from the light source until the polarizing element at an incidence side, the polarized lights are aligned equally in the polarization direction thereof, the amount of heat generation becomes large in the polarizing element at a light exit side when black is displayed totally all over the display.
On the other hand, the liquid crystal display element is, in general, constructed with a driving element of semiconductor and optical function parts or elements, including such as the liquid crystal, and so on. Those, for keeping any one of them function normally, must be kept at temperature lower than a predetermined value (less than 60xc2x0 C., for example). Therefore, cooling is necessary for the liquid crystal display element. As a cooling method for this kind, there were made many proposals in methods of it.
As a conventional art relating to the cooling of the liquid crystal display element, for instance, an example which is described in Japanese Patent Laying-Open No. Hei 3-174134 (1991) is already known. In this conventional art, one of a pair of polarizing plates and the liquid crystal panel as the liquid crystal display element are disposed, being closely contacted with a cooler which contains a cooling liquid hermetically therein. The cooler is hermetically constructed with a frame work and two (2) pieces of transparent plates which closes or covers on both side surfaces of the frame work, and the polarizing plate mentioned above and the liquid crystal panel are closely contacted with the transparent plate, respectively. A part of a heat pipe is inserted into the cooler, and other portion protruding outside the cooler is provided with radiator fins. The heat in the liquid crystal panel and the polarizing panel is transferred to the cooler, further passing through the cooling liquid and the heat pipe, and then it is radiated from the radiator fins to an outside of the cooler.
Further, in the display apparatus described in the above, a part of the light passing through the liquid crystal display element sometimes may happen to be reflected by the optical element, such as a projection lens, behind the liquid crystal element, thereby coming back to the liquid crystal display element. Such the reflection light comes to be a cause of lowering in quality of the projection picture, in particular, such as decrease in contrast thereof.
As a conventional technology for suppressing the decrease in the contrast due to the reflection light from the optical element behind of the liquid crystal display element, other than a measure of improving the transparency (or transmission coefficient) by coating the optical element, there is known another technology which is described in Japanese Patent Laying-open No. Hei 6-110055, for example. With this conventional technology, a so-called xcex/4 plate is positioned between the polarizing plate at the light exit side and the projection lens. The light penetrating through the liquid crystal panel and the polarizing plate at the light exit side reaches through the xcex/4 plate to the projection lens. A portion of this incident light is reflected by the projection lens and comes back into a direction of the liquid crystal panel. At this moment, the reflected light passes through the xcex/4 plate two (2) times after passing through the polarizing plate at the light exit side, on ways of go and back. Therefore, it is rotated by 90 degree in the polarization direction thereof, comparing to that of it when passing through the xcex/4 plate previously. Therefore, the reflection light is unable to pass through the polarizing plate at the light exit side, thereby being absorbed totally therein.
With the conventional technology for protecting the liquid crystal display element from the heating, since the one of the polarizing plates and the liquid crystal display element are positioned so that they are closely contacted with the transparent plates of the cooler which contains the cooling liquid hermetically therein, there are laying two (2) pieces of the transparent plates and the cooling liquid between the polarizing plate and the liquid crystal display element. And, since there occurs reflection due to change in refractive index on each boundary surface of them, the penetration light is easily attenuated therewith.
Further, with this conventional technology, since it is constructed in such manner that the heat generation from the liquid crystal display element is radiated through a large number of heat transmission routes, i.e., the transparent platexe2x80x94cooling liquidxe2x80x94heat pipexe2x80x94radiator finsxe2x80x94peripheral atmosphere (outside air), it is easily affected in the cooling efficiency thereof by an integration or summation of thermal resistance, and is complex in the structure thereof. In particular, for achieving high brightness, there is a necessity of increasing the efficiency in heat radiation, therefore, large-sizing of the heat pipe and/or of the radiator fins are needed.
While, in the above-mentioned conventional technology for suppressing the decrease in the contrast, since it has such the construction that the reflection light from the projection lens is absorbed with the polarizing plate at the light exit side, that polarizing plate at the light exit side is heated up more easily. This heating-up results into a cause of thermal deterioration (including deformation) of the polarizing plate at the light exit side. Further, additional provision of the xcex/4 plate brings an increase in the number of the optical parts and complexity in the structure thereof.
An object of the present invention is, therefore, to provide a liquid crystal display apparatus and an optical device for use therein, achieving a high brightness of picture with a small-sized and simplified structure, as well as suppression of increase in temperature of the liquid crystal display element and the polarizing elements therein.
For achieving the above-mentioned object, in accordance with the present invention, there is provided a liquid crystal display apparatus, comprising:
an optical source system for emitting projection light;
a liquid crystal display portion, for receiving the emission light from said optical source of the optical system and for generating a picture to be projected depending upon a given driver signal;
an optical projection system, including a first optical element which receives a light emitted from said liquid crystal display portion, and for projecting the light emitted from said liquid crystal display portion towards an projection object, wherein said liquid crystal display portion comprises:
a liquid crystal display element for generating the picture;
an incident side polarizing element being positioned at an incident side of said liquid crystal display element;
an exit side polarizing element being positioned at an exit side of said liquid crystal display element;
a holding member for holding at least the liquid crystal display element, the exit side polarizing element and said first optical element; and
a cooling medium, wherein either one of said incident side polarizing element or said liquid crystal display element, said first optical element and said holding member define a space between said liquid crystal display element and said first optical element, and said cooling medium is filled up within said space.
Further, in accordance with the present invention, there is provided a liquid crystal display apparatus, comprising:
an optical source system for emitting projection light;
a plurality of liquid crystal display portions, for receiving the emission light from said optical source of the optical system and for generating a picture to be projected depending upon a given driver signal;
an optical projection system for composing and for projecting the light emitted from said plurality of liquid crystal display portions towards an projection object, wherein:
said optical source system has a light source and an optical separation system for dividing and emitting the light emitted from the light source towards said plurality of liquid crystal display portions; and
said optical projection system has a first optical element for composing lights emitted from said plurality of liquid crystal display portions and a second optical element for projecting the light composed, and further, each of said liquid crystal display portions comprises:
a liquid crystal display element for generating the picture;
an incident side polarizing element being positioned at an incident side of said liquid crystal display element;
an exit side polarizing element being positioned at an exit side of said liquid crystal display element;
a holding member for holding at least the liquid crystal display element, the exit side polarizing element and said first optical element in each of said liquid crystal display portions; and
a cooling medium for cooling, wherein either one of said incident side polarizing element or said liquid crystal display element, said first optical element and said holding member define a space between said liquid crystal display element and said first optical element, and said cooling medium is filled up within said space.
In this instance, said holding member is provided for each of said liquid crystal display portions, and the space within which said cooling medium is filled up is defined for each of said liquid crystal display portions.
Alternatively, said holding member is provided in common for said liquid crystal display portions, and the space within which said cooling medium is filled up is defined as a one space as a whole for said liquid crystal display portions.
Furthermore, in accordance with the present invention, there is provided a liquid crystal display apparatus, comprising:
an optical source system for emitting projection light;
a plurality of liquid crystal display portions, for receiving the emission light from said optical source of the optical system and for generating a picture to be projected depending upon a given driver signal;
a projection optical system for composing and for projecting the light emitted from said plurality of liquid crystal display portions towards an projection object, wherein:
said optical source system has a light source and an optical separation system for dividing and emitting the light emitted from the light source towards said plurality of liquid crystal display portions; and
said optical projection system has a first optical element for composing lights emitted from said plurality of liquid crystal display portions and a second optical element for projecting the light composed, and further, each of said liquid crystal display portions comprises:
a liquid crystal display element for generating the picture;
an incident side polarizing element being positioned at an incident side of said liquid crystal display element;
an exit side polarizing element being positioned at an exit side of said liquid crystal display element;
a holding member for holding at least the liquid crystal display element, the exit side polarizing element and said second optical element; and
a cooling medium for cooling, wherein said holding member is provided in common for said liquid crystal display portions, as well as, in each of said liquid crystal display portions, either one of said incident side polarizing element or said liquid crystal display element, said second optical element and said holding member define a space between said liquid crystal display element and said second optical element, the space within which said cooling medium is filled up is constructed as one space as a whole for the liquid crystal display portions, and said cooling medium is filled up within said space.
Here, said first optical element can be so constructed that it is received within said space.
Moreover, in accordance with the present invention, there is provided an optical device, including a liquid crystal display element within an optical path, comprising:
an incident side polarizing element positioned at an incident side of said liquid crystal display element;
an exit side polarizing element positioned at an exit side of said liquid crystal display element;
fixing means for fixing said incident side polarizing element, said liquid crystal display element and said exit side polarizing element;
cooling medium; and
holding means for holding said cooling medium under a condition of contacting with said exit side polarizing element.
In each invention in the above, according to the present invention, further, the following embodiments can be applied in appropriate.
a) said exit side polarizing element is positioned at an incident surface of said first optical element.
b) said exit side polarizing element is fixed on a surface at an exit side of said liquid display element.
c) said exit side polarizing element is located between said liquid crystal display element and said first optical element and positioned under condition of being apart from both of them.
d) said holding member has openings at the incident side and the exit side, respectively, and further, at said incident side opening is installed any one of said incident side polarizing element and said liquid crystal display element, and at said exit side opening is installed said first optical element.
e) at the incident side opening of said holding member is installed said incident side polarizing element, and said liquid crystal display apparatus is held by said holding member under condition that the cooling medium lies on both surfaces at the incident side and the exit side thereof.
f) at the incident side opening of said holding member is installed said liquid crystal display element, and said liquid crystal display apparatus is held by said holding member under condition that the cooling medium lies on a surf ace s of the incident side thereof.
g) said liquid crystal display portion is held by said holding member under condition that at least said exit side polarizing element contacts with said cooling medium.
h) said cooling medium has a refractive index near to that of said exit side polarizing element.
i) the refractive index of said cooling medium lies within a range from 1.2 to 1.7.
j) said holding member is made of metal and provided with a heat radiation fin.
k) said holding member is made of metal and provided with a pressure adjusting mechanism.
l) said optical source system comprises, an optical source, and an element for converting the light projected from the light source in the polarization thereof, so that the incident light upon said incident side polarizing element comes to be a polarized light including a polarization component being in parallel to a polarization direction of said incident side polarizing element.
With such the liquid crystal display apparatus, it is possible to suppress the increase in temperature of the liquid crystal display element and the polarizing element(s), and also to suppress the change in the refractive index in the optical path at the exit side of the liquid crystal display element down to small.
With suppressing the change in the refractive index down to small, the light reflected back to the liquid crystal display means is reduced down. As a result, high brightness of the picture is accomplished. Further, since there is no necessity of a special optical parts or element such as the xcex/4 plate, and since the structure for the cooling can be simplified with ease and has high efficiency, the apparatus can be small-sized and simplified in the construction as a whole.